Category: Technical

2018 will see the arrival of the all-new Ford Fiesta ST aka the Ultra Mobile and if you listen carefully, you can already hear all the boets fist-pumping in anticipation of this auspicious occasion!

Big news is that this new model is the first ever Ford Performance vehicle to make use of a 1.5-litre 3-cylinder motor and, while sharing a platform with the model it replaces, is the first Fiesta to feature selectable drive modes, enabling steering, engine and stability controls to be configured to Normal, Sport and Track modes. Yoh boet!

Unfortunately, along with the drive modes, we’ll have to put up with Ford’s nauseating and quite frankly miserable Electronic Sound Enhancement Technology which, in short, makes a dreary and depressing come through the vehicle’s speaker system in order to artificially enhance the sound of the engine. We have already been unfortunate enough to endure this in both the 2.3 Ecoboost and 5.0 V8 Mustangs and there’s not much to say really other than no. Just no.

Outputs of 149 kW and 290 N.m. are hugely impressive from a 3-cylinder motor and if you are able to block out Martin Garrix and the shocking sound enhancement, you might even be able to hear a fruity and characterful 3-pot thrum coming from within the engine bay on your sprint from 0-100 km/h which will take 6.7 seconds. A clever little motor, it is also able to shut off one of its cylinders during low-load conditions in order to save fuel, an industry first in a 3-cylinder motor, and thus resulting in emissions as low as 114 g/km.

The current generation Fiesta ST met much praise when launched in 2013 and was even crowned as Top Gear’s Car of the Year 2013. Unsurprisingly then, it still sells in droves to this day thanks to its loyal following of tank top owners and rave-goers. It also has one of the best front-wheel-drive chassis’ money can buy so it’s a good thing then that this will be carried over to the new model.

There is no word on pricing yet but we can expect to see the first units in South Africa during the first half of 2018.

In days gone by, Mercedes-Benz were the last word in refinement. Silky smooth straight sixes were the order of the day and while slightly less practical to package than a V6 motor of equivalent capacity, the inherent benefits of a straight six over a V6 made it worth the long bonnet. Because people hate long bonnets.

It would seem, however, that BMW are the only big manufacturer to produce straight six motors these days. Ford Australia did for a while, but they don’t exist anymore and neither do TVR…

This is strange because while a V6 motor makes packaging a breeze thanks to its compact dimensions, it becomes very complicated due to the inherent vibration issues caused by two banks of cylinders with yaw moments on different axis. Balancing shafts can easily cancel out these vibrations but this means that more inertial mass is required to spin the engine – ie: you need more power.

The great news, then, is that Mercedes-Benz are back on the straight-six train as announced towards the end of 2016 and the new M256 promises to be a powerhouse of note. A part of their new range of modular engines, the new six will arrive alongside petrol and diesel straight-fours, straight-sixes and a petrol V8. They all have identical bore spacing and interfaces to vehicle which cuts production costs.

Back to the M256, it features a host of new technology, most notable of which is the Inline Starter Generator or ‘ISG’. The ISG is a 15kW electric motor which drives the crankshaft, starts the internal combustion engine when start/stop is enabled, recovers energy during coasting and braking and acts as a generator for the 12v electrical system. It can also reduce the load on the engine which aids performance and economy.

It is also part of the 48v electrical system which comprises an electric air-conditioning compressor, electric auxiliary compressor and electric water pump which means there is no need for a belt-driven accessory drive. This means that engine length is reduced which, as I have already mentioned, causes packaging issues with the straight-six motor.

Another brilliant up-side to the whole electrification thing is that the 48v compressor is essentially a supercharger which doesn’t have a parasitic effect on the combustion engine. So at low RPM’s, the compressor kicks in and provides boost up until the big exhaust driven turbo kicks in. Expect figures of around 304 kW (407bhp) and 501 N.m and remarkable efficiency, we hope.

Expect to see this exciting new motor in the updated Mercedes-Benz S-Class before trickling down into the rest of the Mercedes-Benz stable.

Gas flowing, or porting of cylinder heads, is viewed by most laymen as being more mysterious than the US foreign policy. What does it actually mean? How is it done? Does it even work? Of course, there’s no short answer. But hopefully, this article will serve to clear the murky waters somewhat.

The function of the cylinder head, and the inlet ports in particular, is to introduce air from the inlet manifold into the combustion chamber with as little restriction as possible, and hopefully take advantage of the velocity of the fast moving air in some way. The exhaust ports must do the same as they get rid of the burnt products of combustion.

Now, a mass produced cylinder head will have ports which are left “as cast”, so they have a rough finish and various casting flashes which will all cause a disturbance to airflow. They will also often be of a less than optimal shape. This is particularly true of the older designs like the Ford Kent Crossflow or cast iron Chev V8 heads, which have all sorts of undesirable lumps of metal in the wrong places. And you only need a brief glance at an MGB head to see that it’s about as free flowing as a blocked drain. So, with these older heads, it’s a relatively simple matter to remove the offending lumps, and gain a heap of airflow. This is normally done with a pneumatic handheld porting tool or die grinder turning at 5 or 6 thousand RPM, and is extremely easy to make a complete mess of, which would result in the cylinder head being chucked in the bin. For this reason alone, it’s worth leaving it to a professional cylinder head shop. Outfits which habitually do large numbers of the same heads might CNC mill the ports, but in this country, we never see these volumes, so it’s all done by hand.

Generally, after removing metal with an abrasive mounted point or tungsten carbide burr, the ports are polished with fine grit sandpaper, again mounted in a die grinder. The ideal finish of the ports is the subject of much debate – some tuners prefer to leave the intake ports slightly rough, and some prefer a smooth, almost mirror finish. Bench testing seems to indicate there is not much difference to airflow either way.

But what about the size of the ports? Does it make sense just to make them as big as possible before one goes right through the port into the water jacket? No. There is definitely an optimal size, based on the intended speed range of the engine, the capacity of the engine, the valve head size, the camshaft, carburation, etc. In fact, some standard ports are already too big, and more adventurous tuners have filled in these ports with special epoxies. The problem with very large ports is that gas speed drops as a result of the increased port area, and bottom-end power suffers. This may not be an issue in a racing engine which never goes below 4000rpm, but it certainly is in a road car.

The shape of the port is equally important. Material may need to be removed in some places and not in others. Generally one would try to “straighten out” the port as much possible, removing material from the roof of the port and leaving the floor more or less untouched. The area just below the valve seat, called the throat, is also important as it needs to accelerate the gases as they enter the chamber, taking advantage of the venturi effect caused by slightly reducing the cross sectional area of the port just before the exit into the chamber.

The valve seats are then cut using a specialised machine (usually known as a Serdi), giving it a smoother profile and a narrower valve seat which will aid gas flow at small valve openings.

The valve itself is also reshaped to aid gas flow – a particularly critical area, as all the gas must pass over the back of the valve. If one compares a typical valve from 20 years ago to a valve from any modern high-performance car, it is obvious how much development there has been in this regard.

So if all this works on older cars, does that mean it doesn’t work on newer engines? No, of course, it works; it’s just a bit harder, and the gains may not be as big. And if the application is totally different, for example, building a full race engine from a normal road car engine, then bigger valves and bigger ports will be needed to allow the engine to breathe at the higher RPM it will be operating at. There are some exceptions, like an E90 M3 V8, for example, which has big, beautifully-shaped CNC-machined ports, which most sane tuners wouldn’t dare touch.

Measuring the changes in airflow can be done using a device called a flow bench, which measures the flow rate of air through a port at a constant vacuum. It provides a useful yardstick, but is by no means a sure way of predicting the power increase, as the actual conditions in the engine are quite different to what is happening on the flow bench. For example, the vacuum in a combustion chamber is nowhere near constant. It’s also a very time-consuming exercise. And there’s always the infamous story, no doubt greatly exaggerated by now, of a 1950s works Jaguar Le Mans team, which measured each gas-flowed six cylinder head on the flow bench and obviously kept the higher-flowing heads for themselves, selling the others to the customer teams. Imagine their surprise when the customer cars turned out to be faster than the works cars down the Mulsanne straight! Back to the drawing board…

There are other aspects to gas flowing or modifying a cylinder head; one may want to impart a circular motion to the gas as it enters the combustion chamber which will aid cylinder filling. This is known as “swirl”, and is most often associated with 2 valves per cylinder heads.

Obviously, this subject could have several postgraduate theses written about it, so it’s only possible to lightly scratch the surface on these pages, but hopefully it’s enough to enlighten the average armchair enthusiast. Just don’t be tempted to get out your Dremel and start hacking away at your ports on the weekend…

Side Slip Control

Side Slip Control. That sounds like something used to prevent old people from falling down the stairs. It isn’t, trust me it isn’t. Instead, that is the name of a feature found in certain Ferrari’s such as the 458 Speciale. So what is this feature? To put it in its simplest form, this technology allows you to manage and maintain perfect oversteer. To put it simpler, this feature allows you to drift your Ferrari and look good doing it. How? Its all very complicated you see, it uses various things such as the diff, steering angle and a whole lot of other things I feel a man with a P.h.d would need to explain. All you need to know is that it helps you drift and I think that’s awesome enough. Prepare to see this feature in the upcoming 488 GTB which will soon be on the streets in many countries. For instance, most of us love sausages, we don’t want to know how their made as long as they taste good, that’s all. Now let’s see how this stuff works, and for that we need the help of Steve Sutcliffe from Autocar. Enjoy